MIL-STD-1553B is a military standard or set of standards approved for use by all agencies and departments of The Department of Defense. The purpose of the standard is to provide requirements for standardizing internal time division command/response multiplex data bus techniques, which are to be utilized in systems integration of certain subsystems onboard aircraft, ships, and other military vehicles. The standard therefore defines operational criteria for a multiplex data bus, including electrical and functional formats associated therewith. MIL-STD-1553B is included in a handbook entitled "MIL-STD-1553B Multiplex Applications Handbook" which is a public document that can be obtained from The Naval Publications and Form Center at 5801 Tabor Avenue in Philidelphia, Pa. 19120. This handbook is incorporated herein by reference.
The purpose and function of a modem is, of course, well-known in the art. In the past, certain attempts have been made to design dual redundant modems that fully comply with MIL-STD-1553B. Some of the designs have had certain deficiencies, the most common of which is they are difficult to interface with.
In the past, a modem designed in accordance with MIL-STD-1553B has been typically designed to interface with a particular multiplex data bus. Usually, certain operational differences exist between data buses when they are used in connection with different systems subsystems, even though all technically comply with MIL-STD-1553B. The reason for this is that use of a system or systems in different environments can dictate different and sometimes quite unique applications for computer hardware and software. This is reflected by certain unique characteristics in operation of the particular data bus used in connection with the system, and in any modem further used in connection therewith. The modem is therefore generally designed as an integral part of the system, and this makes the modem difficult to use if it is desired to interface one type of system or subsystem with another.
As a practical matter, accomplishing this means that certain design changes must be incorporated into the modem which, in some cases, can be extremely difficult. This usually involves the design and incorporation of additional circuit cards into the modem, for example, and changes of this nature are time consuming and are made further difficult by the fact that MIL-STD-1553B provides somewhat flexible definitions for modem mode code usage. As started above, certain modem designs in the past have been known to have inadequately identified mode code usage, or in some cases MIL-STD-1553B mode codes are not used at all.
This invention provides a built-in interface that is easy to use for adapting a modem constructed in accordance with this invention to different MIL-STD-1553B systems. The invention provides the user with options that make modem adaptability easy to accomplish without need extensive work or redesign. Additional features and advantages of the invention will be presented below.